How do interactions among motor structures contribute to the selection and execution of coordinated eye, head and hand movements? The present program addresses this question with a series of 5 inter-related projects: Project 1, Brainstem-Cerebellar Interactions in Gaze Control (Freedman, PI), asks how the rostral and caudal regions of the fastigial nucleus interact to coordinate eye and head movements in a continuum of possible combinations during targeted gaze shifts. Project 2, Spatial Interaction of Otolith Mediated Collic Reflexes (Gdowski, PI) asks how interactions between the vestibular nuclei and cervical motoneuron pools stabilize the head during linear whole-body translation. Project 3, Interactions in the Corticostriatal Network (Lee, PI), asks how neural interactions between the prefrontal cortex and the striatum incorporate choice and reward history to select the next movement from discrete alternatives. Project 4, Basal Ganglia - Cortical Interactions in Motor Control (Mink, PI) asks how interactions of the globus pallidus, pars interna, with the primary motor cortex and the supplementary motor area, suppress posture and permit movement, or suppress a prepotent movement when an alternative choice is correct. Project 5, Premotor Interactions in Motoric Choices (Schieber, PI), asks how interactions between the head and arm representations of the ventral premotor cortex contribute to discrete choices of which direction to look, which hand to use, and which target to take. Rather than taking the traditional approach of comparing the function of structures studied one at a time, the present program will improve understanding of how seamlessly coordinated motor behavior, influenced by choices made in various behavioral contexts, emerges from the neural interactions among multiple motor structures. Such an improved understanding of the motor system can lead to improved rehabilitative treatment, and improved functional recovery after nervous system injury from diseases such as stroke and head trauma.